Former Rep. Kathy Dahlkemper (D-Pa.) received numerous threats last year, including one from a man who promised to come to her home. He warned the Democrat, who voted yes on healthcare reform, that her “offspring will pay.” Dahlkemper subsequently requested an increase in police patrols around her house.

These threats are some of the more than two dozen detailed in a series of FBI records recently released to The Hill under the Freedom of Information Act (FOIA). According to the records, the FBI opened, investigated and closed at least 26 instances involving alleged threats against lawmakers last year.

The number of threats against members rose significantly in 2010, according to Senate Sergeant at Arms Terry Gainer, who also serves as the head of the U.S. Capitol Police Board.

Nearly half of the cases the FBI opened last year occurred in the weeks surrounding the healthcare debate in March, with many of the investigations directly linking the threat to the controversial healthcare measure, which was signed into law by President Obama on March 23, 2010.

Hours before the Democratic-led House voted on the measure, it was unclear if it had the votes. Some of the calls appeared to be aimed at influencing the fate of the bill.

For example, Rep. Emanuel Cleaver (D-Mo.) got a phone call in his Kansas City office last March from a caller who “threatened to put a bullet in Cleaver’s head if he voted for healthcare reform,” according to FBI records. Cleaver voted yes.

Several lawmakers received threats not only to their own lives, but also to the lives of their families.

Former Rep. Walt Minnick (D-Idaho) received a three-page typewritten letter sent to his office in Meridian, Idaho, last March, according to the FBI. The letter read, “Vote in favor of progressive liberal programs and DIE in the near future or distant future make no mistake we will come for you, take the wife out to dinner risk getting shot, take the kids to soccer practice risk getting shot … ”

Minnick’s office told the FBI that the former lawmaker has family members who play soccer and that the mention of the sport in the letter “was unnerving,” according to the records. Before he received the letter, Minnick — one of the most conservative Democrats to have served in the last Congress — had said he was a firm no on the health bill and later voted against it.

When an office receives a threat, aides and lawmakers are strongly encouraged to report it to the FBI or Capitol Police, who typically launch a joint investigation. Such a probe can take anywhere from several weeks to several months to complete, and in most cases, as listed in the FBI records, will not result in the prosecution of the accused person.

In some instances, the FBI was unable to track down who the caller was, according to the records.

The threats, coupled with the assassination attempt on Rep. Gabrielle Giffords (D-Ariz.), have worried members and raised questions about security on Capitol Hill.

In January, Rep. Jesse Jackson Jr. (D-Ill.) told The Hill that he and some of his colleagues believe that threats against them are not receiving enough investigation.

There have been some successful prosecutions, however.

Late last week, a man who threatened then-Rep. John Boccieri (D-Ohio) last March was sentenced to four months in prison. Boccieri voted to approve healthcare reform.

In a call to former Sen. Jim Bunning (R-Ky.) last February, a man spewed a barrage of profanity in a voice mail message to the senator’s Louisville office, saying, “I’m comin’ after your f—king family. If I lose my health insurance … and my unemployment … I’m comin’ after you, you motherf—ker. You hear me?”

One of the most recent threats occurred last November, according to the records, when a high school student in Idaho emailed Rep. Mike Simpson (R-Idaho) to tell him that he wanted to use his gun on the lawmaker. The student said that he had meant it as a joke, and the government declined to federally prosecute him.